Terry Pratchett - The Science of Discworld II - The Globe

This analysis leads to conclusions like 'It is worth jumping into a lake to save your sister, but not to save your aunt.' And certainly not to save a stranger.

That's the genetic orthodoxy, and like most orthodoxies, it is believed by the orthodox. On the other hand, though: if someone has fallen into a lake, people do not ask 'Excuse me, sir, but how closely related are you to me? Are you, by any chance, a close relative?' before diving in to rescue them. If they are the sort of people who dive in, they do so whoever has fallen into the lake. If not, they don't. Mostly. A clear exception arises when a child falls in; even if they can't swim its parent is then very likely indeed to plunge in to the rescue, but probably would not do so for someone else's child, and even less so for an adult. So the genetic orthodoxy does have a certain amount going for it.

Not much, though. Fisher's mathematics is rather old-fashioned, and it rests on a big -and very shaky - modelling simplification [54] In Fisher's day, this simplification was a great idea, because it made it possible to do the sums. Nowadays, it's a bad idea, for the same reason. You can do them, but you can't put any faith in the answers. . It represents a species by its gene-pool, where all that matters is the proportion of organisms that possess a given gene. Instead of comparing different strategies that might be adopted by an organism, it works out what strategy is best 'on average'.

And inasmuch as individual organisms are represented within its framework at all, which they are only as contributors to the gene-pool, it views competition between organisms as a direct 'me versus thee' choice. A bird that eats seeds is up against a bird that eats worms in a head-to-head struggle for survival, like two tennis-players ... and may the best bird win.

This is a bean-counting analysis performed with a bean-counting mentality. The bird with the most beans (energy from seeds or worms, say) survives; the other does not.

From a complex system viewpoint, evolution isn't like that at all. Organisms may sometimes compete directly -two birds tugging at the same worm, for instance. Or two baby birds in the nest, where direct competition can be fierce and fatal. But mostly the competition is indirect -so indirect that 'compete' just isn't the right word. Each individual bird either survives, or not, against the background of everything else, including the other birds. Birds A and B do not go head-to-head. They compete against each other only in the sense that we choose to compare how A does with how B does, and declare one of them to be more successful.

It's like two teenagers taking driving tests. Maybe one of them is in the UK and the other is in the USA. If one passes and the other fails, then we can declare the one who has passed to be the

'winner'. But the two teenagers don't even know they are competing, for the very good reason that they're not. The success or failure of one has no effect on the success or failure of the other.

Nevertheless, one gets to drive a car, and the other doesn't.

The driving-test system works that way, and it doesn't matter that the American test is easier to pass than the British one (as we can attest from personal experience). Evolutionary 'competition'

mostly works like the driving test, but with the added complication that just occasionally it really is more like a tennis match.

From this point of view, evolution is a complex system, with organisms as entities. Which organisms survive to reproduce, and which do not, are system-level properties. They depend as much on context (American driving test versus British) as on the internal features of the individuals. The survival of a species is an emergent feature of the whole system, and no simple short-cut computation can predict it. In particular, computations based on the frequencies of genes in the gene-pool can't predict it, and the alleged explanation of altruism by gene- frequencies is unconvincing.

Why, then, does altruism arise? An intriguing answer was given by Randolph Nesse in the magazine Science and Spirit in 1999. In a word, his answer is 'overcommitment'. And it is a refreshing and much-needed alternative to bean-counting.

We have said more than once that humans are time-binders. We run our lives not just on what is happening now, but on what we think will happen in the future. This makes it possible for us to commit ourselves to a future action. 'If you fall sick, I will look after you.' 'If an enemy attacks you, I will come to your aid.' Commitment strategies change the face of 'competition'

completely. An example is the strategy of 'mutual assured destruction' as a deterrent for nuclear war: 'If you attack me with nuclear weapons, I will use mine to destroy your country completely.'

Even if one country has many more nuclear weapons, which on a bean-counting basis means that it will 'win', the commitment strategy means that it can't.

If two people, tribes or nations make a pact, and agree to commit support to each other, then they are both strengthened, and their survival prospects increase. (Provided it's a sensible pact. We leave you to invent scenarios where what we've just said is wrong.) Ah, yes, that's all very well, but can you trust the other to keep to the agreement? We have evolved some quite effective methods for deciding whether or not to trust someone. At the simplest level, we watch what they do and compare it to what they say. We can also try to find out how they have behaved in similar circumstances before. As long as we can get such decisions right most of the time, they offer a substantial survival advantage. They improve how well we do, against the background of everything else. Comparison with others is irrelevant.

From a bean-counter's point of view, the 'correct' strategy in such circumstances is to count how many beans you gain by committing yourself, compare that to how many you gain by cheating, and see which pile of beans is biggest. From Nesse's point of view, that approach doesn't amount to a hill of beans. The whole calculation can be sidestepped, at a stroke, by the strategy of overcommitment. 'Stuff the beans: I guarantee that I will commit myself to you, no matter what.

And you can trust me, because I will prove to you, and keep proving it every day that we live, that I am committed at that level.' Overcommitment beats the bean-counters hands down. While they're trying to compare 142 beans with 143, overcommitment has wiped the floor with them.

Nesse suggests that such strategies have had a decisive effect in shaping our extelligence (though he doesn't use that word): Commitment strategies give rise to complexities that may be a selective force that has shaped human intelligence. This is why human psychology and relationships are so hard to fathom.

Perhaps a better understanding of the deep roots of commitment will illuminate the relationships between reason and emotion, and biology and belief.

Or, to put it another way: perhaps that's what gave us an edge over the Neanderthals. Though it would be difficult to find a scientific test for such a suggestion.

When humans overcommit in this manner, we call it 'love'. There is far more to love than the simple scenario just outlined, of course, but one feature is common to both: love counts not the cost. It doesn't care about who gets the most beans [55] Altruism, cooperation and love among humans are not the only examples of evolutionary overcommitment ... as the Librarian well knows. A banana is much better suited to being eaten by an orangutan than it needs to be. The rest of the fruit kingdom doesn't come close. What's in it for other fruit, like the tomato, is that its seeds pass through the animal and are dispersed, complete with a built-in packet of fertiliser. A bean-counting tomato could reduce its level of suitability and still ensure that its seeds, rather than those of the competition, were propagated (the juiciest tomatoes used to be from the plants growing at the sewage farm ...). But an over-committed banana avoids the need to test such fine points. By going over the top, losing its seed-producing capacity entirely and relying on humans to propagate it, it ensures that it wins so comfortably that no competitor even gets a look in. . And by refusing to play the bean-counters'